In non-contact communication systems that have become increasingly used in recent years, such as RFID systems or near field communication systems, an antenna for communications is mounted on each apparatus to enable communications between cellular electronic apparatuses, such as cellular phones, or between a cellular electronic apparatus and a reader-writer.
If such an antenna for noncontact communications is implemented on the back side of a metal member, because the metal member blocks magnetic fields, the antenna cannot communicate with an apparatus, such as a reader-writer, positioned opposite the antenna with respect to the metal member.
An antenna device in which an antenna coil is arranged on the back side of a metal member having a conductive opening is disclosed in Japanese Patent No. 4687832.
FIG. 24(A) is a back view of an electronic apparatus that includes the antenna device illustrated in Japanese Patent No. 4687832. The back of the electronic apparatus is a surface directed to an antenna of a reader-writer that is to communicate therewith (that is a communication partner). FIG. 24(B) is a plan view of the inside of a lower casing on the back side.
As illustrated in FIG. 24(A), a conductive layer 22 is disposed on the outer surface of a lower casing 1. One example of the conductive layer 22 can be a metal-evaporated film made of, for example, aluminum. The conductive layer 22 has an opening CA, and further has a slit SL connecting the opening CA and the outer edge. As illustrated in FIG. 24(B), an antenna coil module 3 partially overlapping the opening CA is arranged on the inner surface of the lower casing 1.
As another example, an antenna coil arranged on its end portion of a communication terminal and enabling communications from both the front and back of the communication terminal is disclosed in Japanese Patent No. 4626413.